The present invention relates to the formation of novel germanosiloxane compounds which can be used as spin-on-glass precursors, optically useful films, and precursors to other germania- and silica- based glass objects. It also relates to a method of forming these objects, including germania-silica based glass films, microlenses, lasers, adhesive layers and other glass objects.
Generally, germanium-oxygen bond containing compounds or germoxanes are synthesized through hydrolysis of germanium halides. Since the germanium-oxygen bond is relatively weak and quite subject to hydrolysis by water, the synthesis of certain polygermoxane compounds has to be carried out under non-aqueous conditions. Recently, certain polygermoxanes with formula (R.sub.1 R.sub.2 GeO).sub.n (n=3-50) were synthesized through reaction between a germanium hydrocarbyl dihalide and a hydrocarbyllithium [U.S. Pat. No. 5,391,792]. Polygermoxanes with formula (RGeO.sub.1.5).sub.n also were synthesized through the photooxidation of polygermynes [W. J. Szymanski, G. T. Visscher, and P. A. Bianconi, Macromolecules, 26, 869(1993)].
Small germoxane compounds have been synthesized through different methods [M. P. Brown and E. G. Rochow, J. Am. Chem. Soc., 82, 4166(1960); H. Puff, S. Franken, W. Schuh, and W. Schwab, J. Organometal Chem., 254, 31(1983); L. Ro.beta. and M. Drager, Z. Naturforsch, 39b, 868(1984); S. Masamune, S. Batcheller, J. Park, W. M. Davis, O. Yamashita, Y. Ohta, and Y. Kabe, J. Am. Chem. Soc., 111, 1889(1989)]. Small germanosiloxane compounds with one or more Ge--O--Si bond have been synthesized [F. Glockling, The Chemistry of Germanium, Academic Press, London(1969); M. Lesbre, P. Mazerolles, and J. Satge, The Organic Compounds of Germanium, John Wiley & Sons, London(1971)]. Other germanosiloxane ring compounds were also synthesized through the reaction of diallylsilanediols and germanium halides [H. Puff, M. Bockmann, T. Kok, and W. Schuh, J. Organometal. Chem., 268, 197(1984); M. Akkurt, T. R. Kok, P. Faleschini, L. Randaccio, H. Puff, W. Schuh, J. Organometal. Chem., 470, 59(1994)].
However, few types of large polygermanosiloxane compounds have been synthesized and applied to the formation of optical materials. It is an object of this invention to provide methods for the synthesis of polygermanosiloxane materials which can be used as germanium-containing Spin-on-Glass (SOG) materials. SOG materials commonly are designed to lead to silica (SiO.sub.2)like characteristics and fall into two categories called p-SOG and s-SOG. Both are based on organosiloxane molecules. Those that are polymeric with inert organic side chains, such as --CH.sub.3, --C.sub.2 H.sub.5, --C.sub.6 H.sub.5, etc. are called p-SOG. Those with reactive side chains, such as --OH, --OCH.sub.3, --OC.sub.2 H.sub.5, --O.sub.2 CH.sub.3, etc., which are capable of reacting with the other molecules to form polymerized SiO.sub.2 -- like materials are called s-SOG. S. Ito, Y. Homma, E. Sasaki, S. Uchimura and H. Morishima, J. Electrochemical Society, Vol. 137, No 4, pp 1212-1218, 1990. However, analogous spin-on-glass materials based on organogermanosiloxanes are less common or not available. It is the object of this invention to introduce germanium into polysiloxanes to form germanium-containing SOG materials.
Electronic and optical systems often require films and other objects to function as dielectrics, waveguides, lenses, filters, lasers and other structures. Commonly they are made of silica-like materials that are formed from organosiloxane or other spin-on-glasses or precursors. The optical and electrical properties of silicas formed this way tend to fall in a limited range near those of amorphous SiO.sub.2 itself. For some purposes, however, it would be advantageous to have analogous glassy materials with a substantially different set of properties, especially higher or lower refractive indices, and varied electrical and optical properties. It also would be valuable to have higher refractive index glasses with incorporated transition metal, lanthanide, actinide or other metal ions. And, it would be valuable to have materials that are chemically suited to interact with germanium-containing substrates including silicon, silica, germanium, and germanium-containing layers. Thus, it is also the object of this invention to provide a method to form germanium dioxide doped silicate glass films and other objects with the types of compositions and on the substrates mentioned above.
These and other objects and features of the invention will be apparent from the following summary and description of the invention and from the claims.